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.TH TCSETATTR 3C "Aug 14, 2002"
.SH NAME
tcsetattr \- set the parameters associated with the terminal
.SH SYNOPSIS
.LP
.nf
#include <termios.h>

\fBint\fR \fBtcsetattr\fR(\fBint\fR \fIfildes\fR, \fBint\fR \fIoptional_actions\fR,
     \fBconst struct termios *\fR\fItermios_p\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBtcsetattr()\fR function sets the parameters associated with the terminal
referred to by the open file descriptor \fIfildes\fR (an open file descriptor
associated with a terminal) from the \fBtermios\fR structure (see
\fBtermio\fR(4I)) referenced by \fItermios_p\fR as follows:
.RS +4
.TP
.ie t \(bu
.el o
If \fIoptional_actions\fR is \fBTCSANOW\fR, the change will occur immediately.
.RE
.RS +4
.TP
.ie t \(bu
.el o
If \fIoptional_actions\fR is \fBTCSADRAIN\fR, the change will occur after all
output written to \fIfildes\fR is transmitted. This function should be used
when changing parameters that affect output.
.RE
.RS +4
.TP
.ie t \(bu
.el o
If \fIoptional_actions\fR is \fBTCSAFLUSH\fR, the change will occur after all
output written to \fIfildes\fR is transmitted, and all input so far received
but not read will be discarded before the change is made.
.RE
.sp
.LP
If the output baud rate stored in the \fBtermios\fR structure pointed to by
\fItermios_p\fR is the zero baud rate, B0, the modem control lines will no
longer be asserted. Normally, this will disconnect the line.
.sp
.LP
If the input baud rate stored in the \fBtermios\fR structure pointed to by
\fItermios_p\fR is 0, the input baud rate given to the hardware will be the
same as the output baud rate stored in the \fBtermios\fR structure.
.sp
.LP
The \fBtcsetattr()\fR function will return successfully if it was able to
perform any of the requested actions, even if some of the requested actions
could not be performed. It will set all the attributes that implementation
supports as requested and leave all the attributes not supported by the
implementation unchanged. If no part of the request can be honoured, it will
return \fB\(mi1\fR and set \fBerrno\fR to \fBEINVAL\fR. If the input and output
baud rates differ and are a combination that is not supported, neither baud
rate is changed. A subsequent call to \fBtcgetattr\fR(3C) will return the
actual state of the terminal device (reflecting both the changes made and not
made in the previous \fBtcsetattr()\fR call). The \fBtcsetattr()\fR function
will not change the values in the \fBtermios\fR structure whether or not it
actually accepts them.
.sp
.LP
The effect of \fBtcsetattr()\fR is undefined if the value of the \fBtermios\fR
structure pointed to by \fItermios_p\fR was not derived from the result of a
call to \fBtcgetattr\fR(3C) on \fIfildes\fR; an application should modify only
fields and flags defined by this document between the call to
\fBtcgetattr\fR(3C) and \fBtcsetattr()\fR, leaving all other fields and flags
unmodified.
.sp
.LP
No actions defined by this document, other than a call to \fBtcsetattr()\fR or
a close of the last file descriptor in the system associated with this terminal
device, will cause any of the terminal attributes defined by this document to
change.
.sp
.LP
Attempts to use \fBtcsetattr()\fR from a process which is a member of a
background process group on a \fIfildes\fR associated with its controlling
terminal, will cause the process group to be sent a \fBSIGTTOU\fR signal. If
the calling process is blocking or ignoring \fBSIGTTOU\fR signals, the process
is allowed to perform the operation, and no signal is sent.
.SH USAGE
.sp
.LP
If trying to change baud rates, applications should call \fBtcsetattr()\fR then
call \fBtcgetattr\fR(3C) in order to determine what baud rates were actually
selected.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fB0\fR is returned. Otherwise, \fB\(mi1\fR is
returned and \fBerrno\fR is set to indicate the error.
.SH ERRORS
.sp
.LP
The \fBtcsetattr()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEBADF\fR\fR
.ad
.RS 10n
The \fIfildes\fR argument is not a valid file descriptor.
.RE

.sp
.ne 2
.na
\fB\fBEINTR\fR\fR
.ad
.RS 10n
A signal interrupted \fBtcsettattr()\fR.
.RE

.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The \fIoptional_actions\fR argument is not a supported value, or an attempt was
made to change an attribute represented in the \fBtermios\fR structure to an
unsupported value.
.RE

.sp
.ne 2
.na
\fB\fBENOTTY\fR\fR
.ad
.RS 10n
The file associated with \fIfildes\fR is not a terminal.
.RE

.sp
.LP
The \fBtcsetattr()\fR function may fail if:
.sp
.ne 2
.na
\fB\fBEIO\fR\fR
.ad
.RS 7n
The process group of the writing process is orphaned, and the writing process
is not ignoring or blocking \fBSIGTTOU\fR.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	MT-Safe, and Async-Signal-Safe
.TE

.SH SEE ALSO
.sp
.LP
.BR cfgetispeed (3C),
.BR tcgetattr (3C),
.BR termio (4I),
.BR attributes (7),
.BR standards (7)
